Not sure if the GT500, stock, is putting down 620rwhp on a Mustang Dyno? Regardless, the additional HP coming from the GT500 (stock) cost you $5k more than the ZL1 (Stock). $5k can get you a lot of HP with proper cooling on the ZL1.

Hahaha awesome meme . New background material worthy.

The base MSRP of the GT500 is cheaper and there is no additional HP coming from any option box you can check off the GT500 order sheet. I thought we've gone over this a million times on this website